Building Abstractions with Data - Hierarchical Data and the Closure Property - Representing Sequences - List operations - higher-order functions, currying
Structure and Interpretation of Computer Programs: JavaScript Edition(Harold Abelson(著)、Gerald Jay Sussman(著)、Julie Sussman(著)、The MIT Press)のChapter 2(Building Abstractions with Data)、2.2(Hierarchical Data and the Closure Property)、2.2.1(Representing Sequences)、List operations、Exercise 2.20の解答を求めてみる。
コード
function stringfy(x) {
return x.toString();
}
function pair(x, y) {
return [x, y];
}
function head(z) {
return z[0];
}
function tail(z) {
return z[1];
}
function list(...args) {
return args.length === 0 ?
null :
pair(args[0], list(...args.slice(1)));
}
function display(x) {
return console.log(x);
}
function is_null(x) {
return x === null;
}
function plus_curried(x) {
return y => x + y;
}
function brooks(f, l) {
function iter(f, l) {
return is_null(l) ?
f :
iter(f(head(l)), tail(l));
}
return iter(f, l);
}
display(brooks(plus_curried, list(3, 4)));
function brooks_curried(l) {
return brooks(head(l), tail(l));
}
display(brooks_curried(list(plus_curried, 3, 4)));
display(
brooks_curried(
list(
brooks_curried,
list(plus_curried, 3, 4)
)
) ===
7
);
display(
brooks_curried(
list(
brooks_curried,
list(
brooks_curried,
list(plus_curried, 3, 4)
)
)
) ===
7
);
入出力結果(Terminal, Zsh)
% node answer2.20.js
7
7
true
true
%